Valvular stenosis is a defect which may be congenital, developing in the foetus and present at birth, or may develop over time, for instance as an effect of some other disorder. For example, mitral valve stenosis in adults is rarely congenital and can occur as a result of rheumatic fever or calcium obstruction in the valve.
Congenital valvular stenosis is found in around one in every 1,000 newborns. In some instances health problems affecting the mother during pregnancy is thought to contribute to the defect. About 5% of all cardiac defects are found to relate to valvular stenosis. Valvular abnormalities are found in children of both sexes, but the vast majority of adult valvular stenosis is found to occur in men. Most adults with Mitral stenosis are women who have suffered rheumatic fever as children.
Reduced valvular function is also experienced in some patients, caused by the valves failing to open fully.
A variety of treatments have been attempted to treat these conditions, including diuretic therapy, anticoagulant therapy and open surgery. More recently, however, balloon valvuloplasty has been performed, both on children and on adults. The procedure is to force the valve open, with the aim that so doing will cure the stenosis and prompt normal valve function. In balloon valvuloplasty, a small balloon tipped catheter is positioned within the valve opening and the balloon then inflated to prise the valve leaflets apart. The balloon has to have an inflated diameter no greater than the diameter of the valve seat in order not to damage the valve. The balloon is then deflated and removed.
In order not to cause trauma or damage to the heart, balloon valvuloplasty must be performed quickly.
Often, balloon valvuloplasty can sure the valve function and thus avoid the need for open heart surgery and valve replacement. It is therefore seen as an important method of treatment.
There is a risk, however, during balloon valvuloplasty that the balloon catheter jumps or slips out of position either out of the heart or into the heart, as a result of heart/valve function as well as of the dynamics of the inflating balloon. Such slippage can either lead to an abortive procedure or to damage of the heart.
Balloon catheter assemblies for a variety of treatments have been disclosed in WO-03/039,628, U.S. Pat. No. 6,129,706, U.S. Pat. No. 7,008,438, EP-0,204,218, US-2005/0,075,662, US-2006/0,167,407, US-2009/0,005,732, U.S. Pat. No. 5,395,331, U.S. Pat. No. 5,720,726, U.S. Pat. No. 5,423,745 and U.S. Pat. No. 7,566,319.